Virtually since the advent of graphical user interfaces for computer systems have applications been available which enable the user to create and edit graphic images, and such applications have achieved an extremely high level of sophistication. In the context of drawing and painting applications, computer monitors are able to display two-dimensional graphic representations of image elements which are inputted or controlled by the user via a pointer or cursor function. Conventionally, the pointer or cursor function is operated by means of a mouse, and the user is able to select from a number of available menus attributes of freehand drawing and painting strokes produced by movement of the mouse, such as pen or brush thickness and ink/paint color. In addition, the user can select and insert objects such as prescribed shapes and drawing/painting elements, text, images, paint fill, etc. Once an image has been produced, the user is able to edit it as desired using a suite of available editing functions, and the final image can then be printed by way of appropriate available printing means. Users of such applications range from, at one end of the scale, a graphic designer using a professional graphic design suite, allowing rendering and manipulation of two-dimensional images of complex 3D objects, to an operator conversing with a client or colleague, who simply wishes to communicate an idea of interest in graphic form. In the latter situation, the operator can sketch an idea using the computer application, and then send the sketch via, for example, electronic mail.
Further advances on the above concept have evolved with the development of computer peripheral devices such as touch screen displays and display overlays, and so-called electronic sketchpads. The latter devices employ sensing digitizer tablets, based on any of a number of alternative sensing technologies such as resistive, capacitive and acoustic techniques. The operator uses an appropriate stylus on the tablet to input freehand strokes, and presses ‘buttons’ on the tablet to select from various objects, attributes and commands, which actions result in strokes and objects appearing in real time in an image on the operator's computer display. This type of system has the evident advantage that it is able to far more closely simulate the graphic designer's desktop environment and drawing tools.